Aortic stenosis is a common form of congenital heart disease with known potential for morbidity and/or sudden death with exercise. The pressure gradient across the aortic valve is the most commonly used clinical descriptor of the severity of aortic stenosis. We hypothesize the myocardial oxygen supply -demand ratio, as determined noninvasively, is a more reliable predictor of symptoms, exercise limitation, and electrocardiographic ST segment changes than the pressure gradient itself.